The invention relates to improvements in pin tumbler combination locks. It is known in the prior art to provide a pin tumbler lock system such as disclosed in U.S. Pat. No. 3,742,744. This patent discloses a primary locking system comprising a plurality of pin tumblers and a secondary locking system comprising opposed sets of lateral blocking pins aligned at right angles to the pin tumblers and adapted to engage in grooves in the key. One major disadvantage to this lock system is that the lateral blocking pins must be positioned between the primary pin tumblers. Thus due to the positioning of the lateral blocking pins between the primary pin tumblers, the prior art locking system has a very limited number of combinations. Still further, another disadvantage to this system is that each of the lateral blocking pins and the bores they are received in have a narrow inner portion connected to a larger second portion in order to prevent the pins from fully extending into and blocking the keyway. Thus due to the different diameters and step of each pin and the corresponding bore, additional machining steps are required for the pins and the cylinder plug. Another disadvantage to this system is that due to the length of the pins, the pins have a tendency to tilt in its chamber. Because of this tendency, the key must have a bevel at its tip in order to overcome the additional resistance caused by the pin's tendency to tilt in its chamber. For the foregoing reasons, there is a need for an improved pin tumbler lock with multiple tumbler combinations which overcomes the aforementioned disadvantages.